The present invention relates to a catheter having a bidirectional check valve proximate the tip for controlling fluid flow into and out of the catheter.
There are many medical requirements for chronic vascular access including neonatal umbilical vein cannulation, hyperalimentation, chemotherapy, permanent intravascular site for portable drug infusion devices, hemodialysis, plasmapheresis, and, repeated blood sampling. These procedures are performed by using either transcutaneous or totally implanted intravascular catheters.
Examples of transcutaneous catheters include the Broviak and Hickman central venous catheters (Evermed, Kirkland, Wash.) as well as many similar products generically termed subclavian catheters. Catheters in this category may be generally described as being plastic or rubber tubes with female luer fittings at one end. Catheter patency is maintained by filling the catheter lumen with a solution containing an anticoagulant (heparin) between uses. Since the anticoagulant consistently diffuses from the lumen and into the bloodstream, the catheter has to be refilled at 2-3 day intervals in order to prevent a clot from forming at the distal tip.
The Shiley Vas-Cath (Shiley, Inc., Irvine, Calif.) is a transcutaneous subclavian catheter which differs from subclavian catheters in that it has a removable lining. In the event that the catheter clots, the lining, which contains the clot, is extracted from the outer sheath and replaced.
Another solution to catheter lumen clotting involves the insertion of a solid flexible plastic rod, called an obturator, into the catheter lumen between uses. The obturator completely occupies the catheter lumen and therefore prevents diffusion of blood components and subsequent formation of a clot.
An alternate obturated design is the Wigness/Anderson U.S. Pat. No. 4,705,501 entitled, "Bidirectional Antireflux Vascular Access System", which features a self-contained flexible obturator which resembles a bladder which runs the length of the catheter lumen and is not removed between uses, but is instead shifted between the "active" state (where the lumen is open) and the "dormant" state (where the lumen is occluded by the obturator).
The advantages offered by an intravascular catheter in which the lumen may be closed and therefore isolated from the blood stream when it is not in use are:
1. It is resistant to occlusion from thrombosis;
2. It decreases the risk of air embolism; and
3. It requires less maintenance (e.g., heparinization and irrigation).
Examples of totally implantable catheters, generically referred to as "ports", include the "Infuse-A-Port" (Shiley-Infusaid, Inc., Norwood, Mass.), the "Q-Port" (Quinton Instrument Co., Seattle, Wash.), and the "Port-A-Cath" (Pharmacia-Deltec, Inc., St. Paul, Minn.). Ports are similar to subclavian catheters except that the female luer fitting is replaced by a metal or plastic manifold which houses the fluid conduits between a rubber access septum and the catheter connector. Although the catheters are routinely filled with a heparin solution between uses, if the time interval between catheter uses is relatively long (weeks instead of days), each therapy session is initiated by blowing a small clot into the vasculature.
Advantages offered by a catheter which furthermore is totally implantable are:
1. Longer useful life due to reduced risk of infection;
2. Fewer recannulations and therefore less discomfort to the patient; and
3. More patient freedom (the patient may shower, bathe or swim without having to perform special catheter maintenance).
Designs featuring removable obturators or replaceable linings cannot be modified to be totally implantable by simply attaching them to a port, since that would require that a relatively large, solid element be passed through the skin, subcutaneous tissue and catheter septum with each use.
In order to achieve total implantability of the previously described Wigness/Anderson obturated catheter, it is attached either to a special manifold (Wigness/Dorman patent application dated Oct. 6, 1987, U.S. Ser. No. 105,740, entitled, "Implantable Intravascular Access System") or two septa--one for the functional lumen, and one which is used for shifting the obturator.
Diffusion or aspiration of blood into the subclavian-type catheters may be prevented by adding a check valve to their intravascular tips. The Dorman U.S. Pat. No. 4,657,536 entitled, "Check Valve Catheter" describes a sleeve type one-way check valve design for this purpose. While this design prevents blood components from clotting the tip, it does not allow withdrawal of a blood sample--a maneuver that is sometimes desirable and commonly carried out with subclavian catheters and ports. A commercially available port with a one-way check valve at the tip is the "Implantofix" (Burron Medical Inc., Bethlehem, Pa.).
One commercially available catheter featuring a slit valve at the tip which allows both aspiration of blood and infusion of fluids and yet precludes the diffusion of blood components into the lumen between therapy sessions is the Groshong Catheter (Catheter Technology Corporation, Salt Lake City, Utah). This catheter is available both as a transcutaneous appliance and also as a port.
The present invention solves many problems associated with the prior art.